// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/disk_cache/simple/simple_index.h"

#include <algorithm>
#include <limits>
#include <string>
#include <utility>

#include "base/bind.h"
#include "base/bind_helpers.h"
#include "base/files/file_enumerator.h"
#include "base/files/file_util.h"
#include "base/logging.h"
#include "base/message_loop/message_loop.h"
#include "base/metrics/field_trial.h"
#include "base/numerics/safe_conversions.h"
#include "base/pickle.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_tokenizer.h"
#include "base/task_runner.h"
#include "base/threading/worker_pool.h"
#include "base/time/time.h"
#include "net/base/net_errors.h"
#include "net/disk_cache/simple/simple_entry_format.h"
#include "net/disk_cache/simple/simple_histogram_macros.h"
#include "net/disk_cache/simple/simple_index_delegate.h"
#include "net/disk_cache/simple/simple_index_file.h"
#include "net/disk_cache/simple/simple_synchronous_entry.h"
#include "net/disk_cache/simple/simple_util.h"

#if defined(OS_POSIX)
#include <sys/stat.h>
#include <sys/time.h>
#endif

namespace {

// How many milliseconds we delay writing the index to disk since the last cache
// operation has happened.
const int kWriteToDiskDelayMSecs = 20000;
const int kWriteToDiskOnBackgroundDelayMSecs = 100;

// Divides the cache space into this amount of parts to evict when only one part
// is left.
const uint32_t kEvictionMarginDivisor = 20;

const uint32_t kBytesInKb = 1024;

// Utility class used for timestamp comparisons in entry metadata while sorting.
class CompareHashesForTimestamp {
    typedef disk_cache::SimpleIndex SimpleIndex;
    typedef disk_cache::SimpleIndex::EntrySet EntrySet;

public:
    explicit CompareHashesForTimestamp(const EntrySet& set);

    bool operator()(uint64_t hash1, uint64_t hash2);

private:
    const EntrySet& entry_set_;
};

CompareHashesForTimestamp::CompareHashesForTimestamp(const EntrySet& set)
    : entry_set_(set)
{
}

bool CompareHashesForTimestamp::operator()(uint64_t hash1, uint64_t hash2)
{
    EntrySet::const_iterator it1 = entry_set_.find(hash1);
    DCHECK(it1 != entry_set_.end());
    EntrySet::const_iterator it2 = entry_set_.find(hash2);
    DCHECK(it2 != entry_set_.end());
    return it1->second.GetLastUsedTime() < it2->second.GetLastUsedTime();
}

} // namespace

namespace disk_cache {

EntryMetadata::EntryMetadata()
    : last_used_time_seconds_since_epoch_(0)
    , entry_size_(0)
{
}

EntryMetadata::EntryMetadata(base::Time last_used_time, uint64_t entry_size)
    : last_used_time_seconds_since_epoch_(0)
    , entry_size_(base::checked_cast<int32_t>(entry_size))
{
    SetLastUsedTime(last_used_time);
}

base::Time EntryMetadata::GetLastUsedTime() const
{
    // Preserve nullity.
    if (last_used_time_seconds_since_epoch_ == 0)
        return base::Time();

    return base::Time::UnixEpoch() + base::TimeDelta::FromSeconds(last_used_time_seconds_since_epoch_);
}

void EntryMetadata::SetLastUsedTime(const base::Time& last_used_time)
{
    // Preserve nullity.
    if (last_used_time.is_null()) {
        last_used_time_seconds_since_epoch_ = 0;
        return;
    }

    last_used_time_seconds_since_epoch_ = base::saturated_cast<uint32_t>(
        (last_used_time - base::Time::UnixEpoch()).InSeconds());
    // Avoid accidental nullity.
    if (last_used_time_seconds_since_epoch_ == 0)
        last_used_time_seconds_since_epoch_ = 1;
}

uint64_t EntryMetadata::GetEntrySize() const
{
    return entry_size_;
}

void EntryMetadata::SetEntrySize(uint64_t entry_size)
{
    entry_size_ = base::checked_cast<int32_t>(entry_size);
}

void EntryMetadata::Serialize(base::Pickle* pickle) const
{
    DCHECK(pickle);
    int64_t internal_last_used_time = GetLastUsedTime().ToInternalValue();
    pickle->WriteInt64(internal_last_used_time);
    pickle->WriteUInt64(entry_size_);
}

bool EntryMetadata::Deserialize(base::PickleIterator* it)
{
    DCHECK(it);
    int64_t tmp_last_used_time;
    uint64_t tmp_entry_size;
    if (!it->ReadInt64(&tmp_last_used_time) || !it->ReadUInt64(&tmp_entry_size) || tmp_entry_size > static_cast<uint64_t>(std::numeric_limits<int32_t>::max()))
        return false;
    SetLastUsedTime(base::Time::FromInternalValue(tmp_last_used_time));
    entry_size_ = static_cast<int32_t>(tmp_entry_size);
    return true;
}

SimpleIndex::SimpleIndex(
    const scoped_refptr<base::SingleThreadTaskRunner>& io_thread,
    SimpleIndexDelegate* delegate,
    net::CacheType cache_type,
    std::unique_ptr<SimpleIndexFile> index_file)
    : delegate_(delegate)
    , cache_type_(cache_type)
    , cache_size_(0)
    , max_size_(0)
    , high_watermark_(0)
    , low_watermark_(0)
    , eviction_in_progress_(false)
    , initialized_(false)
    , init_method_(INITIALIZE_METHOD_MAX)
    , index_file_(std::move(index_file))
    , io_thread_(io_thread)
    ,
    // Creating the callback once so it is reused every time
    // write_to_disk_timer_.Start() is called.
    write_to_disk_cb_(base::Bind(&SimpleIndex::WriteToDisk,
        AsWeakPtr(),
        INDEX_WRITE_REASON_IDLE))
    , app_on_background_(false)
{
}

SimpleIndex::~SimpleIndex()
{
    DCHECK(io_thread_checker_.CalledOnValidThread());

    // Fail all callbacks waiting for the index to come up.
    for (CallbackList::iterator it = to_run_when_initialized_.begin(),
                                end = to_run_when_initialized_.end();
         it != end; ++it) {
        it->Run(net::ERR_ABORTED);
    }
}

void SimpleIndex::Initialize(base::Time cache_mtime)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());

#if defined(OS_ANDROID)
    if (base::android::IsVMInitialized()) {
        app_status_listener_.reset(new base::android::ApplicationStatusListener(
            base::Bind(&SimpleIndex::OnApplicationStateChange, AsWeakPtr())));
    }
#endif

    SimpleIndexLoadResult* load_result = new SimpleIndexLoadResult();
    std::unique_ptr<SimpleIndexLoadResult> load_result_scoped(load_result);
    base::Closure reply = base::Bind(
        &SimpleIndex::MergeInitializingSet,
        AsWeakPtr(),
        base::Passed(&load_result_scoped));
    index_file_->LoadIndexEntries(cache_mtime, reply, load_result);
}

void SimpleIndex::SetMaxSize(uint64_t max_bytes)
{
    // Zero size means use the default.
    if (max_bytes) {
        max_size_ = max_bytes;
        high_watermark_ = max_size_ - max_size_ / kEvictionMarginDivisor;
        low_watermark_ = max_size_ - 2 * (max_size_ / kEvictionMarginDivisor);
    }
}

int SimpleIndex::ExecuteWhenReady(const net::CompletionCallback& task)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    if (initialized_)
        io_thread_->PostTask(FROM_HERE, base::Bind(task, net::OK));
    else
        to_run_when_initialized_.push_back(task);
    return net::ERR_IO_PENDING;
}

std::unique_ptr<SimpleIndex::HashList> SimpleIndex::GetEntriesBetween(
    base::Time initial_time,
    base::Time end_time)
{
    DCHECK_EQ(true, initialized_);

    if (!initial_time.is_null())
        initial_time -= EntryMetadata::GetLowerEpsilonForTimeComparisons();
    if (end_time.is_null())
        end_time = base::Time::Max();
    else
        end_time += EntryMetadata::GetUpperEpsilonForTimeComparisons();
    const base::Time extended_end_time = end_time.is_null() ? base::Time::Max() : end_time;
    DCHECK(extended_end_time >= initial_time);
    std::unique_ptr<HashList> ret_hashes(new HashList());
    for (EntrySet::iterator it = entries_set_.begin(), end = entries_set_.end();
         it != end; ++it) {
        EntryMetadata& metadata = it->second;
        base::Time entry_time = metadata.GetLastUsedTime();
        if (initial_time <= entry_time && entry_time < extended_end_time)
            ret_hashes->push_back(it->first);
    }
    return ret_hashes;
}

std::unique_ptr<SimpleIndex::HashList> SimpleIndex::GetAllHashes()
{
    return GetEntriesBetween(base::Time(), base::Time());
}

int32_t SimpleIndex::GetEntryCount() const
{
    // TODO(pasko): return a meaningful initial estimate before initialized.
    return entries_set_.size();
}

uint64_t SimpleIndex::GetCacheSize() const
{
    DCHECK(initialized_);
    return cache_size_;
}

void SimpleIndex::Insert(uint64_t entry_hash)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    // Upon insert we don't know yet the size of the entry.
    // It will be updated later when the SimpleEntryImpl finishes opening or
    // creating the new entry, and then UpdateEntrySize will be called.
    InsertInEntrySet(
        entry_hash, EntryMetadata(base::Time::Now(), 0), &entries_set_);
    if (!initialized_)
        removed_entries_.erase(entry_hash);
    PostponeWritingToDisk();
}

void SimpleIndex::Remove(uint64_t entry_hash)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    EntrySet::iterator it = entries_set_.find(entry_hash);
    if (it != entries_set_.end()) {
        UpdateEntryIteratorSize(&it, 0);
        entries_set_.erase(it);
    }

    if (!initialized_)
        removed_entries_.insert(entry_hash);
    PostponeWritingToDisk();
}

bool SimpleIndex::Has(uint64_t hash) const
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    // If not initialized, always return true, forcing it to go to the disk.
    return !initialized_ || entries_set_.count(hash) > 0;
}

bool SimpleIndex::UseIfExists(uint64_t entry_hash)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    // Always update the last used time, even if it is during initialization.
    // It will be merged later.
    EntrySet::iterator it = entries_set_.find(entry_hash);
    if (it == entries_set_.end())
        // If not initialized, always return true, forcing it to go to the disk.
        return !initialized_;
    it->second.SetLastUsedTime(base::Time::Now());
    PostponeWritingToDisk();
    return true;
}

void SimpleIndex::StartEvictionIfNeeded()
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    if (eviction_in_progress_ || cache_size_ <= high_watermark_)
        return;
    // Take all live key hashes from the index and sort them by time.
    eviction_in_progress_ = true;
    eviction_start_time_ = base::TimeTicks::Now();
    SIMPLE_CACHE_UMA(
        MEMORY_KB, "Eviction.CacheSizeOnStart2", cache_type_,
        static_cast<base::HistogramBase::Sample>(cache_size_ / kBytesInKb));
    SIMPLE_CACHE_UMA(
        MEMORY_KB, "Eviction.MaxCacheSizeOnStart2", cache_type_,
        static_cast<base::HistogramBase::Sample>(max_size_ / kBytesInKb));
    std::vector<uint64_t> entry_hashes;
    entry_hashes.reserve(entries_set_.size());
    for (EntrySet::const_iterator it = entries_set_.begin(),
                                  end = entries_set_.end();
         it != end; ++it) {
        entry_hashes.push_back(it->first);
    }
    std::sort(entry_hashes.begin(), entry_hashes.end(),
        CompareHashesForTimestamp(entries_set_));

    // Remove as many entries from the index to get below |low_watermark_|.
    std::vector<uint64_t>::iterator it = entry_hashes.begin();
    uint64_t evicted_so_far_size = 0;
    while (evicted_so_far_size < cache_size_ - low_watermark_) {
        DCHECK(it != entry_hashes.end());
        EntrySet::iterator found_meta = entries_set_.find(*it);
        DCHECK(found_meta != entries_set_.end());
        evicted_so_far_size += found_meta->second.GetEntrySize();
        ++it;
    }

    // Take out the rest of hashes from the eviction list.
    entry_hashes.erase(it, entry_hashes.end());
    SIMPLE_CACHE_UMA(COUNTS,
        "Eviction.EntryCount", cache_type_, entry_hashes.size());
    SIMPLE_CACHE_UMA(TIMES,
        "Eviction.TimeToSelectEntries", cache_type_,
        base::TimeTicks::Now() - eviction_start_time_);
    SIMPLE_CACHE_UMA(
        MEMORY_KB, "Eviction.SizeOfEvicted2", cache_type_,
        static_cast<base::HistogramBase::Sample>(
            evicted_so_far_size / kBytesInKb));

    delegate_->DoomEntries(&entry_hashes, base::Bind(&SimpleIndex::EvictionDone, AsWeakPtr()));
}

bool SimpleIndex::UpdateEntrySize(uint64_t entry_hash, int64_t entry_size)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    EntrySet::iterator it = entries_set_.find(entry_hash);
    if (it == entries_set_.end())
        return false;

    UpdateEntryIteratorSize(&it, entry_size);
    PostponeWritingToDisk();
    StartEvictionIfNeeded();
    return true;
}

void SimpleIndex::EvictionDone(int result)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());

    // Ignore the result of eviction. We did our best.
    eviction_in_progress_ = false;
    SIMPLE_CACHE_UMA(BOOLEAN, "Eviction.Result", cache_type_, result == net::OK);
    SIMPLE_CACHE_UMA(TIMES,
        "Eviction.TimeToDone", cache_type_,
        base::TimeTicks::Now() - eviction_start_time_);
    SIMPLE_CACHE_UMA(
        MEMORY_KB, "Eviction.SizeWhenDone2", cache_type_,
        static_cast<base::HistogramBase::Sample>(cache_size_ / kBytesInKb));
}

// static
void SimpleIndex::InsertInEntrySet(
    uint64_t entry_hash,
    const disk_cache::EntryMetadata& entry_metadata,
    EntrySet* entry_set)
{
    DCHECK(entry_set);
    entry_set->insert(std::make_pair(entry_hash, entry_metadata));
}

void SimpleIndex::PostponeWritingToDisk()
{
    if (!initialized_)
        return;
    const int delay = app_on_background_ ? kWriteToDiskOnBackgroundDelayMSecs
                                         : kWriteToDiskDelayMSecs;
    // If the timer is already active, Start() will just Reset it, postponing it.
    write_to_disk_timer_.Start(
        FROM_HERE, base::TimeDelta::FromMilliseconds(delay), write_to_disk_cb_);
}

void SimpleIndex::UpdateEntryIteratorSize(EntrySet::iterator* it,
    int64_t entry_size)
{
    // Update the total cache size with the new entry size.
    DCHECK(io_thread_checker_.CalledOnValidThread());
    DCHECK_GE(cache_size_, (*it)->second.GetEntrySize());
    cache_size_ -= (*it)->second.GetEntrySize();
    cache_size_ += entry_size;
    (*it)->second.SetEntrySize(entry_size);
}

void SimpleIndex::MergeInitializingSet(
    std::unique_ptr<SimpleIndexLoadResult> load_result)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    DCHECK(load_result->did_load);

    EntrySet* index_file_entries = &load_result->entries;

    for (std::unordered_set<uint64_t>::const_iterator it = removed_entries_.begin();
         it != removed_entries_.end(); ++it) {
        index_file_entries->erase(*it);
    }
    removed_entries_.clear();

    for (EntrySet::const_iterator it = entries_set_.begin();
         it != entries_set_.end(); ++it) {
        const uint64_t entry_hash = it->first;
        std::pair<EntrySet::iterator, bool> insert_result = index_file_entries->insert(EntrySet::value_type(entry_hash,
            EntryMetadata()));
        EntrySet::iterator& possibly_inserted_entry = insert_result.first;
        possibly_inserted_entry->second = it->second;
    }

    uint64_t merged_cache_size = 0;
    for (EntrySet::iterator it = index_file_entries->begin();
         it != index_file_entries->end(); ++it) {
        merged_cache_size += it->second.GetEntrySize();
    }

    entries_set_.swap(*index_file_entries);
    cache_size_ = merged_cache_size;
    initialized_ = true;
    init_method_ = load_result->init_method;

    // The actual IO is asynchronous, so calling WriteToDisk() shouldn't slow the
    // merge down much.
    if (load_result->flush_required)
        WriteToDisk(INDEX_WRITE_REASON_STARTUP_MERGE);

    SIMPLE_CACHE_UMA(CUSTOM_COUNTS,
        "IndexInitializationWaiters", cache_type_,
        to_run_when_initialized_.size(), 0, 100, 20);
    // Run all callbacks waiting for the index to come up.
    for (CallbackList::iterator it = to_run_when_initialized_.begin(),
                                end = to_run_when_initialized_.end();
         it != end; ++it) {
        io_thread_->PostTask(FROM_HERE, base::Bind((*it), net::OK));
    }
    to_run_when_initialized_.clear();
}

#if defined(OS_ANDROID)
void SimpleIndex::OnApplicationStateChange(
    base::android::ApplicationState state)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    // For more info about android activities, see:
    // developer.android.com/training/basics/activity-lifecycle/pausing.html
    if (state == base::android::APPLICATION_STATE_HAS_RUNNING_ACTIVITIES) {
        app_on_background_ = false;
    } else if (state == base::android::APPLICATION_STATE_HAS_STOPPED_ACTIVITIES) {
        app_on_background_ = true;
        WriteToDisk(INDEX_WRITE_REASON_ANDROID_STOPPED);
    }
}
#endif

void SimpleIndex::WriteToDisk(IndexWriteToDiskReason reason)
{
    DCHECK(io_thread_checker_.CalledOnValidThread());
    if (!initialized_)
        return;
    SIMPLE_CACHE_UMA(CUSTOM_COUNTS,
        "IndexNumEntriesOnWrite", cache_type_,
        entries_set_.size(), 0, 100000, 50);
    const base::TimeTicks start = base::TimeTicks::Now();
    if (!last_write_to_disk_.is_null()) {
        if (app_on_background_) {
            SIMPLE_CACHE_UMA(MEDIUM_TIMES,
                "IndexWriteInterval.Background", cache_type_,
                start - last_write_to_disk_);
        } else {
            SIMPLE_CACHE_UMA(MEDIUM_TIMES,
                "IndexWriteInterval.Foreground", cache_type_,
                start - last_write_to_disk_);
        }
    }
    last_write_to_disk_ = start;

    index_file_->WriteToDisk(reason, entries_set_, cache_size_, start,
        app_on_background_, base::Closure());
}

} // namespace disk_cache
